High voltage circuit breakers with contact pressure boosters and arcing contacts



3,177,33 2 ggu'mc'r PRESSU R. W. BETHKE UIT BREAKERS WITH April 6, 1965,j- ILQQ Y QLTAGE CIRC QYBOOSTERS AND ARCING CONTAC 3 Sheets-Sheet 1Filed June 11 1962 INV EN TOR.

A ril 6, 1965 R. .BETHKE 3,177,332-

HIGH VOLTAGE CIRCUIT AKERS WITH CONTACT PRESSURE BODSTERS AND ARCINGCONTACTS 3 Sheets-Sheet 2 Filed June 11 1962 INVENTOR. PayMa/vp 5 FIJ'JM MM April 6, 1965 R. w. BETHKE 3,177,332

HIGH VOLTAGE CIRCUIT BREAKERS WITH CONTACT PRESSURE BOOSTERS AND ARCINGCONTACTS Filed Jul 18 11, 1962 3 Sheets-Sheet 3 INVENTOR. Rn Mo/vu 21/.BETH/(E United States Patent HIGH VOLTAGE CKRCUH BREAKEM WHTH 08 N- Thisinvention relates to circuit brea ers and more particularly to thecontact structure for high voltage circuit breakers.

High voltage circuit breakers of the type having contacts which part inair and magnetic or gas blast means for blowing an are into interruptingstructure, are generally provided with main current carrying contactsand auxiliary arcing contacts. The auxiliary arcing contacts arenormally connected in shunt with the main current carrying contacts andare arranged to part after the main current carrying contacts haveparted so that the arc will be carried by the auxiliary contacts. Inaddition, such auxiliary contacts are arranged to engage upon closure ofthe circuit breaker prior to the engagement of the main current carryingcontacts so that any pre-strike will also be carried by these auxiliarycontacts. This insures that the main current carrying contacts will notbeco he damaged by repeated arcings.

In order to insure that no arc is struck between the main currentcarrying contacts, the auxiliary contacts should remain in engagementuntil after the main current carrying contacts have separated apredetermined distance. One method of accomplishing this result is tomount one of the auxiliary contacts for pivotal movement toward theother and to employ a relatively large contact pressure spring to holdthe auxiliary contacts in engagement for a short portion of the switcharms pivotal movement.

This prior art arrangement had the disadvantage that the auxiliarycontact spring pressure had to be relatively large, because once themain current carrying contacts part the auxiliary contact carries theentire load current, so that the electromagnetic contact blow-apartforces are substantially increased. Such high contact pressures inhibitrapid closing of the circuit breaker and exert an inordinate force onthe circuit breaker latching mechanism.

it is an object of the invention to provide high voltage circuit breakerhaving auxiliary arcing contacts wherein the spring pressure increasessubstantially when the main current carrying contacts part and whichdecreases sharply upon the re-engagement of these contacts.

Another object of the instant invention is to provide auxiliary arcingcircuit breaker contacts when their contact pressure is relatively highafter the main current carrying contacts have parted and which issubstantially lower when the circuit breaker is in its latched position.

A more specific object of the invention is to provide a circuit breakerwith a pair of contact assemblies mounted for movement into and out of aclosed position and each having a main current carrying contact and anauxiliary arcing contact, wherein one of the contact assemblies includesa contact member for supporting its auxiliary contact and which ismounted for limited translational and pivotal movement toward the otherassembly and spring means are provided for urging the aum'liary contactsinto high pressure engagement when the assemblies are in a closedposition so that relative movement of said assemblies toward an openposition allows initial translational movement of the contact member andpivotal movement thereof upon the termination of translational movementice and after the separation of the main current carrying contacts tohold the auxiliary contacts in engagement, whereby the spring meansbegins acting through a moment arm around the pivotal axis of thecontact member to increase the force holding the auxiliary contactstogether.

These and other objects and advantages or" the instant invention willbecome more apparent from the detailed description thereof taken withthe accompanying drawings in which:

FIG. 1 shows a portion of a circuit breaker illustrating how the contactstructure, according to the instant invention, may be employed;

FIG. 2 is a side elevational view, partly in section, of contactstructure according to the instant invention;

FIG. 3 is a top plan view of the contact shown in FIG. 2;

FIG. 4 shows the contact structure during a switch opening operation;

FIG. 5 is a front view of the contact structure with parts broken away;

FlG. 6 is a perspective view of a component of the contact structureshown in FIGS. 2-5; and

FIGS. 7 and 8 illustrate an alternate embodiment of the instantinvention.

Referring to the drawings in greater detail, FIG. 1 shows a circuitbreaker designated generally by the reference numeral 1%), and includingcontact structure 12 and schematically illustrated arc interruptingstructure 14. The contact structure 112 includes a stationary contactassembly is carried at the inner end of a stud 17 which is supported onthe circuit breaker frame 13, and a movable contact assembly 20 carriedat the upper end of a switch arm 22. The switch arm 22 is pivotallymounted at its lower end on the inner end of a second stud 23.

Each of the studs 17 and 23 carries a disconnect contact 24 and 25,respectively, at its outer end for engagement with coacting disconnectcontacts (not shown) which connect the circuit breaker Ill to the systembeing protected. This establishes a series circuit through the devicedefined by the stud 17, the stationary contact assembly 16, the movablecontact assembly 29, the switch arm 22, and the stud 23. It will beunderstood that a suitable switch operating mechanism, which is notshown but is well known in the art, will be connected to the switch arm22 by a link 6 so that the switch arm 22 may be pivoted clockwise fromits closed position shown by full lines in FIG. 1 to an open positionshown by dotted lines.

It will also be understood by those skilled in the art that uponseparation of the contact structure 12, an arc will be struck betweenthe stationary contact assembly 16 and the movable contact assembly 20.Means (not shown) such as a magnetic coil and/ or gas blast structurewill be provided for blowing the are up into the interrupting structure14 where it is extinguished.

Referring now to FIGS. 2, 3, 4- and 5, the stationary contact assembly36 is shown to include a conductive base 28 secured to the inner end ofthe stud 17 and a pair of arms 29 integral with and extending from thebase 23. A contact member 31 is mounted between arms 2? by means of afirst pin 33 extending therebetween and through an elongate aperture orslot 34 in the member 31 and through a pair of elongate apertures orslots 35 in the arms 2%. While the apertures 34 and 35 are shown to beelongate they may have any suitable configuration such as circular solong as they are oversized relative to the pin 33. The contact member 31also has an oversized aperture 43 formed adjacent its lower end belowthe slot 34. Aperture 43 loosely receives a second pin 44 which alsoloosely extends through an oversized aperture 45 formed in the arms 29.

The contact member 31 consists of a shaped body of conductive materialhaving an auxiliary arcing contact 38 formed at its upper end and a maincurrent carrying contact 39 formed at its lower end. High conductivityinserts 4t) and 41, composed of a material such as silver, are providedat the auxiliary contact 38 and the main current carrying contact 39respectively. Three contact spring assemblies 46, 47 and 48 extendbetween the base 28 and the rear surface of the contact member 31. Eachof the spring assemblies is shown in FIG. 2 to include a spring 58 whoseleft end resides in and bears against a recess 52 formed in the base 23and whose right end bears against the head 53 of a spring guide 54. Thespring guides 54 each include a rod-like body portion which extends backfrom the head 53 toward the recesses 52 and are disposed interiorly oftheir respective springs 58. The right ends of the spring guides 54, asviewed in FIG. 2, each have a bore 55 formed therein which istelescopically received over the body of a pivot base 58. Each pivotbase 58 has a conical head 60 and a reverse conical recess 62 formed atthe point of the head 60 to provide a bearing surface for receiving thehead of a pivot pin 63. The spring guides 54 and pivot bases 58 and thepivot pins 63 prevent the springs Stl from buckling as the contactmember 31 moves.

The movable contact assembly 23 includes a main current carrying contact70 for cooperatively engaging the stationary current carrying contact 39and a movable arcing contact 71 for engaging the stationary arcingcontact 38 when the switch arm 22 is in its closed position as shown inFIGS. 1 and 2. Inserts 77 and '76 are also provided in the currentcarrying contact 71) and the arcing contact 71 respectively of themovable contact assembly 20.

In the event that the contact structure according to the instantinvention is required to carry relatively heavy currents, additionalmain current carrying contacts may be provided. In the illustratedembodiment of the instant invention these may take the form of a pair ofcontact plates 85), see FIGS. 3-6, mounted adjacent the outer surfacesof the arms 29 by the pins 33 and 44 and each of which has an inwardlydirected contact car 82 having an insert 83 mounted thereon. In order toaccommodate these additional main current carrying members the movablemain current carrying contact '70 will be elongate and provided with aplurality of inserts 77. While the pins 33 and 44 will normally securethe contact members 80 so that the cars 82 will be in firm engagementwith the movable main current carrying contacts 7 8 when the latter isin its closed position, a contact pressure spring 84, see

FIG. 4, may be provided between the rear of each of the ears 82 and arecess 85 formed in the arms 29 to insure firm electrical engagement inthe event there is some loosening of the members during operation. Inaddition, retaining rings 86 and 89 aflixed to the ends of the pins 33and 14 and engaging the outer surfaces of the members 80 hold theassembly together.

When the contact assembly is in its closed position, current must betransferred from the arms 29, which are integral with the base 28, tothe contact members 31 and 80 which are movably mounted relativethereto. For this purpose an annular groove 87 is formed in each side ofthe contact member 31 and encompassing the pin 33. A similar annulargroove 88 is formed in each of the outer surfaces of the arms 29.Disposed in each of these annular recesses is a helically wound currentinterchange spring 90. As seen in FIG. 5, the distance between thebottom of the recesses 87 and 88 and the opposite surfaces of the arm 29and the contact member 83 respectively, is less than the normal outsidehelical diameter of the springs 93 so that each of the convolutions ofsaid springs are forced to lay over at an angle relative to theirhelical axes. As a result of the resiliency of the springs 90, eachconvolution bears in firm electrical engagement with their recesses andthe opposed conductive surface to provide a current path therebetween.Thus, a large number of parallel current paths are provided between thearms 29 and the contact members 31 and to form a low friction highcurrent capacity joint therebetween. For a more detailed description ofthe current interchange structure just described, reference is made tocopending application Serial No. 847,263, filed October 19, 1959 nowPatent No. 3,056,101 and assigned to the assignee of the instantinvention.

It can be seen in FIG. 2 that when the contact structure 12 is in itsclosed position the line of action of the upper spring assembly 46,acting through its associated pivot pin 63, will be through the contactmember 31 at a point above the slot 34. The line of action of the middlespring assembly 47 will be through the contact member 31 at a pointslightly below the center of the slot 34 and the line of action of thelower spring assembly 48 will be through the contact member 31 at apoint slightly below the axis of the recess 43. Thus, it will beappreciated that when the switch arm. 22 is in its closed position,substantially the entire force of the upper spring assembly 46 will acton the arcing contact 38 and substantially the entire force of the lowerspring assembly 43 will act on the main current carrying contact 39,while the force of spring assembly 47 will be split between the two.

It can be seen from FIGS. 2 and 3 that when the contact arm 22 is in itsclosed position, the pin 33 will be intermediate the slots 35 in thearms 29 and adjacent the right end of the slot 34 in contact member 31.In addition, the pin 44 is substantially in the center of the aperture43 in the contact member 31 and the apertures 45 in the arms 29. As theswitch arm 22 begins pivoting away from the stationary contact assembly16, during a switch opening operation, the contact assembly 20 willbegin moving toward the right as viewed in FIG. 2. This will allow thespring assemblies 46, 47 and 48 to translate the contact member 31toward the right so that the arcing contact 38 and the main currentcarrying contact 39 remain in engagement with their counterparts '71 and70 respectively in the movable contact 20.

After the contact member 31 has moved a short distance toward the right,the left side of the aperture 43 in the contact member 31 will engagethe pin 44 and move it into engagement with the right side of theapertures 45 in the arms 29. As a result, further forward movement ofthe lower end of the contact member 31 will be prevented. However,because the slot 34 in contact member 31 is substantially longer thanthe diameter of the apertures 43 and 45, the pin 33 will be at a pointintermediate the ends of the slot 34. Such forward movementof thecontact member 31 will also move the left edge of the slot 34 towardengagement with the pin 33. As a result, the contact member 31 willbegin pivoting around the lower pin 44.

As the contact member 31 begins pivoting clockwise about the pin 44, thestationary main current carrying contacts 39 and 82 will disengage fromthe movable main current carrying contacts 70. However, such pivotalmovement of the contact member 31 allows the stationary arcing contact38 to remain in engagement with the movable arcing contact 71 as seen inFIG. 4.

It will be appreciated that at this point all of the current will now beflowing through the arcing contacts 38 and 71 so that theelectromagnetic force tending to blow them apart will be substantiallyincreased over that which existed when the major portion of this currentwas carried by the main current carrying contacts. As a result, asubstantially greater spring force is necessary to hold these arcingcontacts in engagement.

This additional spring force, which is required only during a switchopening operation and when the main current carrying contacts haveparted, is supplied by two factors. Firstly, the force of the upperspring assembly 46, which formerly acted directly on the arcing contact38, new acts through a moment arm equal to the distance from the centerof pin 44 to its line of action. As a result, the force exerted by thespring assembly 46 acting through this moment arm, providessubstantially greater contact pressure and this increase occurs at themoment that the main current carrying contacts part. Secondly, the forceexerted by the center spring assembly 47, which was formerly splitbetween the arcing contact 38 and the main current carrying contact 39,is now all transferred to the arcing contact 38. It can be seen too thatthis tranfer of the entire force of the center spring assembly 47 to thearcing contact 38 will also occur at the moment that the contact member36 begins pivoting and the main current carrying contacts part.

Clockwise pivotal movement of the contact 31 will continue until theleft end of the slot 34% engages the pin 33 and moves said pin intoengagement with the right end of the slots 35 in the arms 29. Upon thisevent the contact member 31 will come to rest and the arcing contacts 38will be disengaged from the movable arcing contact 71 and any arc strucktherebetween will be extinguished in the arc extinguishing structure 14,in a manner Well known in the art.

While the switch is in its open position the contact member 31 willremain in its pivoted position shown in FIG. 4. As a result, movement ofthe switch blade 22 toward its closed position will cause the movablearcing contact 71 to engage the stationary arcing contact 33 so that anyprestrike, which would occur if the device were closed under load, wouldbe drawn through these arcing contacts.

After the arcing contacts engage, the contact member 31 will berotatedcounterclockwise around the pin 44 until the main current carryingcontacts 39, 70 and 32 engage. Further movement of the switch blade 22will move the contact member 31 toward the left compressing the springassemblies 46, 47 and 48 until the contact member 31 is returned to itsinitial position as shown in FIG. 2.

It will be appreciated also that this increase contact pressure will theavailable .at the arcing contact 38 during a switch closing operationand will exist until contact between the main current carrying contactsis re-established at which time the normal and substantially smallercontact pressure required to hold the arcing contacts closed will bere-established. Thus, when the switch is in its closed position, thecontact pressure at the arcing contacts will be substantially smallerthan that available during a switch opening or switch closing operation.As a result a substantially smaller strain will be placed on the circuitbreaker mechanism for holding the contacts 12 closed.

In the alternate embodiment of the invention shown in FIGS. 7 and 8, thecontact member 31 is divided into two mirror image portions 31a and 31bto provide an additional point of engagement at the main currentcarrying and arcing contacts for increased current carrying capacity.This construction requires that the portions 31a and 31b beindependently pivotable to allow for uneven contact wear. As a result, aTeflon sheet 95 is disposed between the portions 31a and 31b to permitlow-friction relative sliding movement. In addition, a yoke 96 isprovided between each of the spring assemblies 46, 47 and 48 and thecontact portions 31a and 31b to divide the spring pressures between thetwo.

As seen more particularly in FIG. 8 each yoke 96 consists of a U-shapedmember having an car 97 extending from the base of each of its legs. Asmall aperture 98 formed in the back of each of the portions 31a and 31band adjacent their upper ends loosely receives the ears 97 While thebase of one leg of the yoke 96 bears against each of said portions. Ahole 99 in the central portion of the yoke 96 receives the truncatedpivot pin 63a.

The various other elements of the contact portions 31a and 31bcorrespond to the elements of the contact memher 31 and accordingly willnot be discussed in detail for the sake of brevity, it being sufiicientto state that such corresponding elements are identified bycorresponding numerals which are distinguished by the letters a or b.

While only a few embodiments of the invention have been shown anddescribed, it is intended that the invention not be limited thereto, butonly by the scope of the appended claims.

I claim:

1. A pair of contact assemblies mounted for movement into and out of aclosed position, one of said contact assemblies having a main currentcarrying contact and an auxiliary arcing contact, the other of saidcontact assemblies including a base member and a contact member, a firstaperture formed in each of said members, a first in means extendingthrough each of said apertures and being loosely received in at leastone of them to mount said contact member on said base member for limitedtranslational and pivotal movement toward said other assembly, a secondaperture formed in each of said members and a second pin means extendingthrough said second apertures and being loosely received in at least oneof them for limiting the pivotal movement of said contact member, a maincurrent carrying contact mounted on said contact member and beingdisposed adjacent its pivotal axis and an auxiliary contact mountedthereon and being remotely disposed from said axis, a first spring meansoperatively engaging said contact member at a point adjacent saidpivotal axis and a second spring means operatively engaging said memberat a point remote from said axis, said spring means urging the maincurrent carrying and auxiliary contacts into high pressure engagementwhen said assemblies are in a closed position with said pins inintermediate positions within the apertures which loose ly receive them,relative movement of said assemblies toward an open position allowingtranslational movement of said contact member until said first pin meansengages the margin of said first apertures whereupon pivotal movementthereof commences to separate said main current carrying contacts and tohold said auxiliary contacts in engagement so that said second springmeans acts through a moment arm around the pivotal axis of said contactmember to increase the pressure holding said auxiliary contactstogether, said pivotal movement being arrested upon the engagement ofsaid second pin means between the margins of said second apertures.

2. The contact assemblies set forth in claim 1, wherein said contactmember comprises two side-by-side portions, each of said portionsincluding an auxiliary contact and a main current carrying contact, andwherein each of said spring means including yoke means for dividing thecontact pressure between each of said portions.

3. The contact assemblies set forth in claim 1 wherein said first andsecond pin means are loosely received in the apertures in each of saidmembers, and including a pair of contact elements one of which isdisposed on each of the opposite sides of said other contact assemblyand en gaging the opposite ends of said first and second pin means, andspring means urging said contact elements into engagement with the maincurrent carrying contacts of said one contact assembly when saidassemblies are in a closed position.

4. The contact assemblies set forth in claim 3, wherein currentinterchange spring means is disposed between said members and saidcontact elements to provide a low frictional current path therebetween.

References Cited by the Examiner UNITED STATES PATENTS 2,717,292 9/55Frink et al. 200-144 BERNARD A. GILHEANY, Primary Examiner.

1. A PAIR OF CONTACT ASSEMBLIES MOUNTED FOR MOVEMENT INTO AND OUT OF ACLOSED POSITION, ONE OF SAID CONTACT ASSEMBLIES HAVING A MAIN CURRENTCARRYING CONTACT AND AN AUXILIARY ARCING CONTACT, THE OTHER OF SAIDCONTACT ASSEMBLIES INCLUDING A BASE MEMBER AND A CONTACT MEMBER, A FIRSTAPERTURE FORMED IN EACH OF SAID MEMBERS, A FIRST PIN MEANS EXTENDINGTHROUGH EACH OF SID APERTURES AND BEING LOOSELY RECEIVED IN AT LEAST ONEOF THEM TO MOUNT SAID CONTACT MEMBER ON SAID BASE MEMBER FOR LIMITEDTRANSLATIONAL AND PIVOTAL MOVEMENT TOWARD SAID OTHER ASSEMBLY, A SECONDAPERTURE FORMED IN EACH OF SAID MEMBERS AND A SECOND PIN MEANS EXTENDINGTHROUGH SAID SECOND APERTURES AND BEING LOOSELY RECEIVED IN AT LEAST ONEOF THEM FOR LIMITING THE PIVOTAL MOVEMENT OF SAID CONTACT MEMBER, A MAINCURRENT CARRYING CONTACT MOUNTED ON SAID CONTACT MEMBER AND BEINGDISPOSED ADJACENT ITS PIVOTAL AXIS AND AN AUXILIARY CONTACT MOUNTEDTHEREON AND BEING REMOTELY DISPOSED FROM SAID AXIS, A FIRST SPRING MEANSOPERATIVELY ENGAGING SAID CONTACT MEMBER AT A POINT ADJACENT SAIDPIVOTAL AXIS AND A SECOND SPRING MEANS OPERATIVELY ENGAGING SAID MEMBERAT A POINT REMOTE FROM SAID AXIS, SAID SPRING MEANS URGING THE MAINCURRENT CARRYING AND AUXILIARY CONTACTS INTO HIGH PRESSURE ENGAGEMENTWHEN SAID ASSEMBLIES ARE IN A CLOSED POSITION WITH SAID PINS